The present invention relates generally to an apparatus and method for directing a laminar flow of a fluid along the surface of a planar substrate. In particular, the apparatus of the present invention is utilized to coat a substrate by means of a chemical vapor deposition process by directing a laminar flow of a gaseous reactant mixture toward the surface of the substrate to cause the reactant mixture to deposit the desired coating on the substrate surface.
Chemical deposition processes such as pyrolytic processes and hydrolytic processes are well known in the art of coating substrates. The physical form of the coating reactants employed in such processes may be liquid, vapor, liquids or solids dispersed in gas mixtures, aerosols, or vaporized or vaporous coating reactants dispersed in gas mixtures.
One of the problems associated with coating substrates by directing a gaseous reactant mixture along a substrate surface to deposit the coating relates to maintaining a uniform thickness of the coating along the substrate. In certain instances, such as the application of a reflective metal oxide coating to a sheet of glass, the requirement that the coating have a uniform thickness is especially important since small variations in the coating thickness can result in the glass sheet having poor optical quality. For example, variations in thickness of the metal oxide coating of one millionth of an inch can produce an undesirable optical effect or an unaesthetic appearance in the glass. Generally, in order to produce a coating having a constant thickness, it is necessary that the gaseous reactant mixture be uniformly applied to the entire sheet of glass.